Water pollution in New Zealand

Water pollution in New Zealand is an increasing concern for those who use and care for waterways and regulatory bodies. An increase in population is linked to an increase in water pollution, due to a range of causes such as rural land use, industrial use and urban development. Fresh water quality is under pressure from agriculture, hydropower, urban development, pest invasions and climate change. While pollution from point sources has been reduced, diffuse pollution such as nutrients, pathogens and sediments development and from stormwater in towns is not under control. There are more than 800 water quality monitoring sites around New Zealand that are regularly sampled.

Guideline standards for water quality are published by MfE.

Agriculture is a major use of lowland areas of New Zealand and has had an impact on water quality. The expansion of intensive dairy production has resulted in greater levels of nitrogen in soil, surface and groundwater.

In 1993, the National Institute of Water and Atmospheric Research summarised available data on the quality of water in rivers. They concluded that "Some lowland river reaches in agriculturally developed catchments are in poor condition" reflecting "agriculturally derived diffuse and point source waste inputs in isolation or in addition to urban or industrial waste inputs". The key contaminants identified in lowland rivers were dissolved inorganic nitrogen, dissolved reactive phosphorus, sediment and coliforms. Small streams in some dairy farming areas such as the Waikato and Canterbury were identified as being in relatively poor condition.

Sediment from erosion of hills and river banks is also a source of pollution of waters. The sediments loading from high intensity, increasing frequency storm and high rainfall events has led to millions of tonnes of sediment changing fluvial systems in NZ waterways. This sediment contains high organic contents from forest litter which is changing sedimentation patterns and increasing organic bed loads and deposition in NZ lakes and shallow coastal waters.

Since 2005 increased dairy farming rates of grazing animals have outstripped riparian planting and the ability of some Regional councils to manage and mitigate impacts on the quality of water., and there is some evidence of urea use leading to nitrogen levels in waterways. Horticulture, arable farming and plantation forestry generally have a lesser impact than dairy farming.

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